Yes, I agree that the resistor is often better, but what if your device
needs to draw a large current periodically, and is not operating at that
much voltage overhead (deriving 5v from 8v using an LDO reg,for example).
Then, I don't think that a large enough resistor to protect the  diode is
practical. I guess the only real choice in these cases (other than the
fuse) is a more sophistocated method,such as the FET.

Sean

At 08:22 AM 6/1/99 +1000, you wrote:
>Jim Paul wrote:
>
>> You could add a diode across the batteries with a fuse so that is the
>> batteries are inserted the wrong way, the fuse blows cutting off the
>> power source.
>
>  But then your appliance has "failed".  Not good publicity.  OK, if it
>is used under supervision and can be repaired and put back into service.
>Better to use a resistor (only need a few ohms) and diode.
>
>  Reverse-inserted batteries promptly go flat.  "Darn batteries!"
>Properly inserted ones last for "ages".  Appliance always works if
>good batteries inserted correctly.  This is the "teaching" approach.
>--
>  Cheers,
>        Paul B.
>
|
| Sean Breheny
| Amateur Radio Callsign: KA3YXM
| Electrical Engineering Student
\--------------=----------------
Save lives, please look at http://www.all.org
Personal page: http://www.people.cornell.edu/pages/shb7
mailto:shb7@cornell.edu ICQ #: 3329174
________________________________________________________
NetZero - We believe in a FREE Internet.  Shouldn't you?
Get your FREE Internet Access and Email at
http://www.netzero.net/download/index.html